Polyester latex provides toner with desirable rheologic properties in fusing and low minimum fix temperature. But polyester toner has a relatively high production cost. Moreover, polyester toners are sensitive to RH. Humidity impacts triboelectric charge of the polyester toner particles, which in turn, impacts xerographic performance and image quality.
Polystyrene/acrylate toners have higher melting temperature but have a relatively lower cost of production.
Hybrid toners have been prepared, for example, by blending 10% of polystyrene/butyl acrylate latex with polyester latex via nominal aggregation coalescence processes (U.S. Ser. No. 14/561,543). In other methods, hybrid toner was prepared having a styrene/butyl acrylate shell over a core of both polyester and styrene/butyl acrylate resins using a continuous coalescence process (US Pub. No. 20150118610) or where the core was comprised of styrene/acrylate resin and a polyester shell by a two step aggregation coalescence process (U.S. Pat. No. 9,046,801).
Preparation of each of those hybrid toners requires complicated subsequent aggregation coalescence or continuous coalescence process adjustments to blend the styrene/acrylate into emulsion aggregation (EA) toners, which is costly and inefficient.
Accordingly, there remains a need to blend poly(acrylate/styrene) and polyester resins in toner to stabilize charge and to capitalize on the desirable rheologic properties of polyester resins. That problem was addressed herein by preparing hybrid latex using a novel semi-continuous emulsion polymerization method forming interpenetrating polymer networks (IPN's) of the styrene/acrylate resin in hydrated polyester resin seed particles. The IPN method provides a unique way to combine intimately polyester and poly(acrylate/styrene) polymers by permanent interlocking of entangled polymer chains.